Seals, such as axial seals for bushings, are commonly used in the endless tracks of track-type earthmoving vehicles. In relatively clean environments, a small amount of inward radial load is required on the sealing lip to seal in the bearing lubricant. However, as the operating environment becomes dirtier and more severe, higher lip loads are required to ensure good sealability and to keep the abrasive contaminants out.
The track bushings used in the endless tracks of earthmoving vehicles and the radial lip seals used in the pin joints of the loader linkages of earthmoving vehicles present one of the most severe operating environments possible for these kind of seals. In such extremely severe applications, abrasive contaminants such as mixtures of sand, dirt and water enter the joint and become lodged under the seal lip. Abrasives lodged under the seal lip quickly grind a groove into the pin/bushing and/or the seal and quickly wear out the seal lip and consequently the pin/bushing. This wear mechanism is the primary mechanism controlling the life of the seal.
The track bushings in the hinge joints of the endless tracks of earthmoving vehicles require a face seal to be subjected to a very high axial force in order to prevent the highly abrasive contaminants from being lodged under the seal lip. In radial lip seals, garter springs have been frequently employed about the seal lip to increase the inward radial load on the lip so as to enhance its sealing ability. Unfortunately, increasing axial force acts to limit the amount of lubricant reaching the contact surface, accelerating the deterioration of the seal.
What is needed is a mechanical seal that seals properly and is resistant to wear. Such a seal should be able to perform in very severe environments, such as those found in earthmoving applications.